1. Field of the Invention
The present invention relates to a tracking control apparatus for determining the orientation of a solar radiation receiver device, which especially could be a solar concentrator which can be directionally-controlled in relation to two coordinates, to a light source which is moving relative to that device and including a sensor whose optical axis is oriented toward the light source in a fixed spatial correspondence to the tracking control apparatus, and specifically to the tracking of solar concentrators in relation to two coordinates.
2. Description of the Prior Art
Solar concentrators having a high concentration ratio of 300 or more must track the sun with a high precision of better than 0.1.degree. in order to operate with the desired efficiency. For this purpose, the solar radiation energy must, as much as possible, travel at all times without loss from the concentrator to the radiation receiver, and a tracking control apparatus is provided to track the movement of the sun in two axes throughout the day.
In theory, this tracking can be done by a fixed control program which is based on the predetermined movement of the sun. However, since operational variations can occur as a result of tolerances in bearings and transmissions, imprecise erection, errors in the position control components, in the angular control and as a result of wind, a tracking control apparatus is generally provided which is directly dependent on the incidences of light.
It is known in the prior art to provide tracking control apparatus including a number of light-sensitive cells and shadow columns for precision adjustment, which operate with sufficient sensitivity in clear weather and experience a deterioration in performance in the presence of fog, clouds and mist. Their tracking accuracy is only about 0.2.degree. (12'), which is not sufficient for high-concentration ratio solar radiation receivers.
Examples of optical position sensing equipment and devices are shown in "Automatische Lageerkennung mit optoelektronischen Empfangern".
An example of an optical control arrangement is shown in British Pat. No. 1,312,663 which corresponds to German Laid Open Application No. 21 26 702.
Examples of positioning systems are found in U.S. Pat. Nos. 4,267,497; 4,221,995; 4,093,154; 4,000,449; and 3,949,582, all of which are incorporated herein by reference.